Method for desulphurising a gaseous mixture containing H2 S and SO.sub.

Abstract

A single-stage low temperature catalytic process for desulphurisation of a gas which contains a mixture of H 2 S and SO 2 which process includes feeding the gas to be treated at a temperature below the dew point of sulphur to a Claus converter having a Claus catalyst in a reaction stage in which the catalyst includes a composite catalytic mass of alumina and one or more compounds of titanium, yttrium, lanthanum or the rare-earth elements of atomic number 58 to 71, and contacting the gas with the Claus catalyst at a temperature below the dew point of sulphur, by which sulphur deposits on the Claus catalyst and the gas is desulphurised.

We claim: 
     
       1. A low temperature catalytic process for desulphurisation of a gas which contains a mixture of H 2  S and SO 2  in a 2:1 molar ratio in a low overall concentration less than 6% by volume, the process comprising: a) feeding the gas to be treated at a temperature below the dew point of sulphur to a Claus converter containing Claus catalyst in a reaction stage, said catalyst being a calcined catalytic mass having at least a portion which consists essentially of alumina and one or more titanium compounds in which the overall weight content of the titanium compounds is in the range of 1 to 20% of the sum of said overall weight content and of the weight of the alumina, the catalytic mass being a sulphur trap for the deposited sulphur,   b) contacting the gas to be treated with the Claus catalyst in the reaction stage for H 2  S to react with SO 2  at a temperature below the dew point of sulphur, thereby forming sulphur which deposits on the Claus catalyst and desulphurising said gas,   c) releasing said desulphurised gas, and   d) regenerating the Claus catalyst by purging the catalyst with a non-oxidizing gas at a temperature between 200° C. and 500° C. and vaporizing the sulphur retained on the catalyst.   
     
     
       2. The process of claim 1 wherein the catalytic mass constitutes all of the catalyst promoting the Claus reaction. 
     
     
       3. The process of claim 1 wherein the catalytic mass has a specific surface, determined by the BET nitrogen adsorption method, of between 80 and 400 m 2  /g. 
     
     
       4. The process of claim 3 wherein said specific surface is between 120 and 400 m 2  /g. 
     
     
       5. The process of claim 1 wherein the residence time of the gas mixture to be desulphurised in the presence of the catalyst promoting the Claus reaction, determined under normal pressure and temperature conditions, ranges from 1 to 15 seconds. 
     
     
       6. The process of claim 5 wherein said residence time ranges from 3 to 10 seconds. 
     
     
       7. The process of claim 1 wherein the temperature at which step (b) is performed is also higher than the dew point of water in the reaction mixture resulting from the contact with the catalyst. 
     
     
       8. The process of claim 1 wherein the dew point of sulphur is about 185° C. 
     
     
       9. The process of claim 1 wherein the temperature at which step (b) is performed is in the range of 120° C. to 170° C. 
     
     
       10. The process of claim 1 wherein the catalyst constitutes all of the catalyst promoting the Claus reaction and of alumina and one or more titanium compounds. 
     
     
       11. The process of claim 1 wherein the overall weight of the titanium compounds represents 2 to 18% of the sum of said overall weight content and of the weight of alumina. 
     
     
       12. The process of claim 11 wherein the overall weight of the titanium compounds represents 3% to 16% of the sum of said overall weight content and of the weight of alumina. 
     
     
       13. The process of claim 12 wherein the overall weight of the titanium compounds represents 5% to 10% of the sum of said overall weight content and of the weight of alumina. 
     
     
       14. The process of claim 1 wherein the overall concentration of H 2  S and SO 2  is between about 0.05% to 6.0% by volume. 
     
     
       15. The process of claim 14 wherein the overall concentration of H 2  S and SO 2  is between about 0.05% to 2.0% by volume. 
     
     
       16. The process of claim 1 which further comprises, after regenerating the catalyst, cooling the regenerated Claus catalyst to a temperature below the dew point of sulphur with an inert gas having a temperature lower than about 160° C. 
     
     
       17. The process of claim 1 wherein the one or more titanium compounds consist of titanium oxide. 
     
     
       18. A low temperature catalytic process for desulphurisation of a gas which contains a mixture of H 2  S and SO 2  in a low overall concentration less than 6% by volume, the process comprising: a) feeding the gas to be treated at a temperature below the dew point of sulphur to a Claus converter containing Claus catalyst in a reaction stage, said catalyst being a calcined catalytic mass at least a portion which consists essentially of alumina and titanium oxide in which the overall weight content of the titanium oxide is in the range of 1 to 20% of the sum of said overall weight content and of the weight of the alumina, the catalytic mass being a sulphur trap for the deposited sulphur,   b) contacting the gas to be treated with the Claus catalyst in the reaction stage for H 2  S to react with SO 2  at a temperature below the dew point of sulphur, thereby forming sulphur which deposits on the Claus catalyst and desulphurising said gas,   c) releasing said desulphurised gas, and   d) regenerating the Claus catalyst by purging the catalyst with a non-oxidizing gas at a temperature between 200° C. and 500° C. and vaporizing the sulphur retained on the catalyst.   
     
     
       19. The process of claim 18 wherein the overall weight of the titanium compounds represents 2 to 18% of the sum of said overall weight content and of the weight of alumina. 
     
     
       20. The process of claim 19 wherein the overall weight of the titanium compounds represents 3 to 16% of the sum of said overall weight content and of the weight of alumina. 
     
     
       21. The process of claim 20 wherein the overall weight of the titanium compounds represents 5% to 10% of the sum of said overall weight content and of the weight of alumina. 
     
     
       22. The process of claim 18 wherein the overall concentration of H 2  S and SO 2  is between about 0.05% to 6.0% by volume. 
     
     
       23. The process of claim 22 wherein the overall concentration of H 2  S and SO 2  is between about 0.05% to 2.0% by volume. 
     
     
       24. The process of claim 18 which further comprises, after regenerating the catalyst, cooling the regenerated Claus catalyst to a temperature below the dew point of sulphur with an inert gas having a temperature lower than about 160° C. 
     
     
       25. The method of claim 18 wherein the desulphurized gas is released to the atmosphere. 
     
     
       26. The method of claim 18 wherein the regeneration of the catalyst is performed with the desulphurised gas. 
     
     
       27. The method of claim 18 wherein the reaction temperature is in the range of 120° C. to 170° C. 
     
     
       28. The process of claim 18 wherein the composite catalytic mass constitutes all of the catalyst promoting the Claus reaction. 
     
     
       29. The process of claim 18 wherein the H 2  S and SO 2  are present in the mixture in about a 2:1 molar ratio. 
     
     
       30. A low temperature catalytic process for desulphurisation of a gas which contains a mixture of H 2  S and SO 2  in a low overall concentration less than 6% by volume, the process comprising: a) feeding the gas to be treated at a temperature below the dew point of sulphur to a Claus converter containing Claus catalyst in a reaction stage, said catalyst being a calcined catalytic mass having at least a portion which consists essentially of alumina and titanium compounds in which the overall weight content of the titanium compounds is in the range of 1 to 20% of the sum of said overall weight content and of the weight of the alumina, the catalytic mass being a sulphur trap for the deposited sulphur,   b) contacting the gas to be treated with the Claus catalyst in the reaction stage for H 2  S to react with SO 2  at a temperature below the dew point of sulphur, thereby forming sulphur which deposits on the Claus catalyst and desulphurising said gas, and   c) allowing the desulphurised gas to flow away from the catalyst.   
     
     
       31. The process of claim 30 wherein the composite catalytic mass constitutes all of the catalyst promoting the Claus reaction. 
     
     
       32. The process of claim 30 wherein the overall concentration of H 2  S and SO 2  is between about 0.05 and 6.0% by volume. 
     
     
       33. The process of claim 32 wherein the H 2  S and SO 2  are present in the mixture in about a 2:1 molar ratio. 
     
     
       34. The process of claim 30 wherein the one or more titanium compounds consist of titanium oxide. 
     
     
       35. The process of claim 30 wherein the residence time of the gas mixture to be desulphurised in the presence of the catalyst promoting the Claus reaction, determined under normal pressure and temperature conditions, is in the range from 1 to 15 seconds. 
     
     
       36. The process of claim 30 wherein the composite catalytic mass has a specific surface, determined by the BET nitrogen adsorption method, of between 80 and 400 m 2  /g.